Cell adhesions, cell junctions and extracellular structures Flashcards

1
Q

Epithelium

A

sheets of cells that are
polarized, with discrete functional
domains at opposite ends (apical and
basal) of the cells.

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2
Q

Connective tissue

A

more loosely
organized, in which cells are attached
to each other, a rigid scaffold, or both

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3
Q

Cell-Cell Junctions

A

Specialized structures where
two cells come together are
called cell-cell junctions

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4
Q

Type of animal cell junctions

A
  • Adhesive junctions
  • Tight junctions
  • Gap junctions
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5
Q

plant junctions

A

Plant cells have special structures
called plasmodesmata

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6
Q

cell table

A
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7
Q

Adhesive Junction

A

Link adjoining cells
* Adhesion proteins are key
* Some need a linker protein
* Cadherins
* Are dynamic

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8
Q

Types of adhesive junctions interactions

A

Homophilic interactions: same
* Heterophilic interactions: different

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9
Q

Cadherin characterisation

A

“Repeats” in their extracellular domain
➢ A transmembrane domain.
➢ Varying cytosolic ends.

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10
Q

E-cadherins

A

E-cadherins are found on epithelial cells

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11
Q

P-cadherins

A

P-cadherins in placenta (and other tissues)

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12
Q

Cadherin function

A
  • The amount and type of cadherins on cell surfaces help
    segregate cells into specific tissues.
  • Cadherin expression is essential for organization of cells during
    development
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13
Q

Desmosomes

A

Provide a tissue with structural
integrity
* The desmosomal cadherins are
called desmocollins and
desmogleins.
* Linker protein = planktoglobin

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14
Q

cell-cell adhesions for cellular events

A
  • Lectins
  • Cell adhesion molecules
    (CAMs)
  • Selectins – e.g. Leukocyte
    adhesion during
    inflammation.
    insert
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15
Q

Tight Junctions

A

Seal the gap between
adjacent epithelial
cells

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16
Q

Tight junction protein types

A

Proteins include:
➢occludin
➢junctional
adhesion
molecules (JAMs)
➢claudins

17
Q

Gap Junctions

A
  • Allow direct electrical & chemical communication
  • Connexons form 3 nm wide channels
18
Q

ECM types

A

bone
Cartlidge
Connective tissue

19
Q

Bone

A

Rigid ECM with few
interspersed cells

20
Q

Cartlidge

A

More flexible than bone

21
Q

Connective tissue

A

Gelatinous with
interspersed fibroblasts

22
Q

Three Classes of ECM Molecules

A
  1. Structural proteins → collagens & elastins
  2. Protein-polysaccharide complexes → proteoglycans
  3. Adhesive glycoproteins →fibronectins & lamins
23
Q

collagen

A
24
Q

Elastin

A
25
Q

Proteoglycans

A

glycoproteins where many glycosaminoglycans
(GAGs) attach to a single protein

26
Q

Adhesive Glycoproteins

A

Adhesive Glycoproteins Anchor Cells to the
Extracellular Matrix
* Direct links between the ECM and the plasma membrane are
reinforced by a family of adhesive glycoproteins
* They have multiple domains to bind molecules in the ECM and
receptors on membranes
* Laminins and fibronectins

27
Q

Fibronectins

A
  • Glycoproteins in the ECM
  • Many isoforms exist
  • 2 subunits connected by SS
    bonds
  • Rod-like domains bind specific
    ECM molecules / cell surface
    receptors
28
Q

Laminins

A

Glycoprotein
* Bind cells to the basal lamina

29
Q

Basil lamina

A
  • Basil lamina = structural support & barrier
  • Cells can alter properties of the basil
    lamina
  • Matrix metalloproteinases degrade local
    ECM at the basil lamina
30
Q

Laminin structure

A
31
Q

Integrins

A
  • Cell surface receptors → bind ECM
    constituents
  • Transmembrane proteins with α&β domain
  • Many isoforms:
  • α5β1 binds fibronectin
  • α6β1 binds laminin
32
Q

Hemidesmosomes

A
  • In epithelial cells
  • α6β4 integrin
  • Attach to laminin in the basil lamina; to keratin in the cytoskeleton
33
Q

Anchorage-dependant growth

A
34
Q

Anchorage independent growth

A
35
Q

paracellular transport and barrier

A
36
Q

tight junction structure

A
37
Q

Leukocyte rolling

A

Lectins allow leukocytes to roll on top of epithelial cells instead of just free-floating by being passed from one cell to another
-selectin expression is increased by inflation
insert

38
Q

Focal adhesions

A